/*THE 嘘解法*/

#include<bits/stdc++.h>

using namespace std;

struct I{I(){ios::sync_with_stdio(false);cin.tie(0);}}init;

typedef vector<int> V;
typedef vector<V> Graph;

bool dfs(int v,int depth,Graph &G,vector<int> &used,vector<int> &near){
    if(v==0)return false;
    if(depth==4)return near[v]==1;
    else{
        for(auto &u:G[v]){
            if(used[u]==0){
                used[u]=1;
                if(dfs(u,depth+1,G,used,near))return true;
                used[u]=0;
            }
        }
    }
    return false;
}
int main(){
    int N,M;
    cin>>N>>M;
    vector<int> A(M),B(M);
    for(int i=0;i<M;A[i]--,B[i]--,i++)cin>>A[i]>>B[i];
    Graph g(N);
    for(int i=0;i<M;i++){
        g[A[i]].push_back(B[i]);
        g[B[i]].push_back(A[i]);
    }
    vector<int> dist(N,-1);
    dist[0]=0;
    queue<int> que;
    que.push(0);
    while(que.size()){
        int v=que.front();que.pop();
        if(dist[v]<=1)
            for(auto &u:g[v]){
                if(dist[u]==-1){
                    dist[u]=dist[v]+1;
                    que.push(u);
                }
            }
    }
    Graph G(N);
    for(int i=0;i<M;i++)if(dist[A[i]]!=-1&&dist[B[i]]!=-1){
        G[A[i]].push_back(B[i]);
        G[B[i]].push_back(A[i]);
    }
    vector<int> near(N,0);
    for(auto &v:G[0])near[v]=1;
    vector<int> used(N,0);
    for(auto &v:G[0]){
        used[v]=1;
        if(dfs(v,1,G,used,near)){
            cout<<"YES"<<endl;
            return 0;
        }
        used[v]=0;
    }
    cout<<"NO"<<endl;
    
    return 0;
}